NASA's SWOT Satellite Captures First-Ever Large River Waves from Space.

In a groundbreaking achievement, scientists from NASA and Virginia Tech have successfully used satellite technology to observe and measure large river waves—temporary flood surges that can pose significant threats to communities. Utilizing data from the Surface Water and Ocean Topography (SWOT) satellite, the team documented three distinct flood waves traveling through rivers in the United States, a feat never before accomplished from space.

These observed waves, according to the researchers, were likely driven by intense rainfall events and the sudden release of water caused by an ice jam. The findings demonstrate the potential of satellite-based monitoring to revolutionize flood forecasting, particularly in regions lacking sufficient infrastructure like levees and flood gates.

Unlike ocean waves, which are formed by wind and tides and move with rhythmic consistency, river waves—also referred to as flood or flow waves—are irregular and temporary. They often result from heavy rain or melting snow and can stretch for tens or even hundreds of miles. These waves play a natural role in transporting nutrients and organisms but can also lead to severe flooding when intensified by extreme weather or structural failures.

"Ocean waves are familiar to us through surfing and boating, but rivers are the lifelines of the planet. Understanding their behavior is crucial," said Cedric David, a hydrologist at NASA's Jet Propulsion Laboratory and co-author of the study published May 14 in Geophysical Research Letters.

The study’s lead author, doctoral researcher Hana Thurman of Virginia Tech, examined data from SWOT, a satellite mission launched in 2022 by NASA and France's space agency CNES. Equipped with a sophisticated Ka-band Radar Interferometer (KaRIn), SWOT measures water surface elevation by sending microwaves to Earth’s surface and calculating their return time. While previously used to track rising sea levels, tsunami waves, and even map the ocean floor, Thurman explored whether SWOT could also detect river wave anomalies.

Her research uncovered three striking examples. The first occurred in April 2023 on the Yellowstone River in Montana, where SWOT recorded a 9.1-foot (2.8-meter) wave crest moving toward the Missouri River. This event, including a dramatic 6.8-mile (11-kilometer) peak followed by a trailing wave, was likely triggered by the sudden breakup of an upstream ice jam, as confirmed through Sentinel-2 satellite imagery.

Two additional waves were linked to rainfall runoff. On January 25, 2024, SWOT detected a massive 30-foot (9-meter) wave on the Colorado River near Austin, Texas—the largest flood recorded there that year. This wave traveled over 250 miles (400 kilometers) to Matagorda Bay at a speed of about 3.5 feet (1.07 meters) per second and extended 166 miles (267 kilometers) in length.

The third wave originated on Georgia’s Ocmulgee River near Macon in March 2024. Measuring over 20 feet (6 meters) tall and spanning more than 100 miles (165 kilometers), it moved at roughly 1 foot (0.33 meters) per second over a 124-mile (200-kilometer) course.

“This study is helping us understand the form and movement of river waves over long distances,” Thurman said. “It could provide answers to critical questions like how quickly a flood might arrive and whether existing infrastructure is at risk.”

Traditionally, river waves have been monitored using stream gauges positioned at fixed locations. While effective, these networks—maintained in the U.S. by agencies like the U.S. Geological Survey—are limited in coverage, especially internationally. George Allen, Thurman’s advisor and a remote sensing expert, emphasized that satellite data acts as a valuable supplement. “If gauges are like toll booths tracking cars, SWOT is the helicopter giving a broader view of traffic.”

SWOT’s satellite-based wave speed measurements closely matched those from ground gauges, confirming the satellite's reliability. With SWOT orbiting Earth several times daily, it is projected to observe more than half of all large flood events during some stage of their development.

Source:https://phys.org/news/2025-05-swot-satellite-large-scale-river.html

This is non-financial/medical advice and made using AI so could be wrong.